BRPI1000995A2 - process of desulphurization of a gaseous effluent, comprising an in-line analysis and control device - Google Patents

Abstract

DESULFURATION PROCESS OF A GASEOUS EFFLUENT, BEHAVIORING AN IN-LINE ANALYSIS AND CONTROL DEVICE. The present invention relates to a process of desulfurization of a gaseous effluent, containing sulfuric hydrogen, which uses a Claus treatment unit followed by a Clauss waste gas treatment unit (TGT), this process comprises the use of a online analysis of the H2S / S02 ratio at the output of the TGT unit and a regulation circuit, allowing to maintain that H2S / S02 molar ratio at the output of the TGT unit at a value close to 2 and generally between 1.5 and 2.5 .

Description

Report of the Invention Patent for "PROCESSODE OF DISULFURING A WASTE WASTE, BEHAVIORING AN ONLINE ANALYSIS AND CONTROL DEVICE".

The present invention relates to the field of sulfur containing gas treatment, and more precisely to gas treatment, by applying Claus sandblasting. It refers more particularly to an improved process of treating a gaseous effluent containing sulfur hydrogen, this process allows maximizing the sulfur yield of the Clause chain, thereby producing a purified gas generally containing less than 1% of sulfur. elemental sulfur volume, even less than 0,5 or 0,1% by volume of elemental sulfur.

The present invention may be advantageously applied to treat gases from hydrodesulfurization, catalytic cracking or natural gas purification units.

The invention relates to an improved desulfurization process of a gaseous effluent containing sulfur hydrogen using a Claus treatment unit followed by a tail gas treatment unit (tail gas treatment or TGT according to Anglo-Saxon terminology). process comprising an in-line analyzer at the exit of the TGT unit of the H2S / SO2 molar ratio (equal to the volume percentages of these compounds in the gas phase) and a regulating circuit, allowing this H2S / SO2 molar ratio to be maintained at output of the TGT unit at a value close to 2 and generally between 1.5 and 2.5.

Prior Art

Several methods may be applied to eliminate sulfur hydrogen in a gas to be treated. Such methods are described, for example, in FR-A-2 411 802 and FR-A-2 336 163.

The Claus process is widely applied to recover elemental sulfur from gaseous fillers containing sulfur hydrogen (H2S). However, the smoke emitted by the plants of Type Claus units contains, even after several catechitic stages, negligible quantities of acid gases. Therefore, it is necessary to treat these effluent or Claus unit waste gases (called "tail gas" according to Anglo-Saxon thermology) to eliminate most toxic compounds in order to comply with anti-pollution standards. These standards are becoming increasingly stringent and existing technology needs to be permanently improved.

It is known, for example, to recover from a Claus unit approximately 95% by weight of the elemental sulfur present in the gases to be treated. Further treatment of effluent from a Claus unit (eg a Clauspol® unit) achieves, for example, 99.8% by weight of recovered sulfur. The Claus reaction is well known, in a Claus unit, sulfur hydrogen (H2S) reacts on sulphurous anhydride (SO2), according to the reaction:

2 H2S + SO2 3S + 2 H2O

To ensure optimum sulfur elimination yield to eliminate side reactions, it is preferable to maintain the H2S / SO2 molar ratio as close as 2, according to the Claus reaction stoichiometry.

In the case of the Clauspol® process, this reaction is applied in a reaction medium consisting of an organic solvent and a catalyst comprising an alkaline or alkaline earth salt of an organic acid. The reaction is generally countercurrent in a contactor reactor and its temperature is controlled by passing the solvent which has been drawn into the lower end of the reactor by a circulation pump in a heat exchanger. favor the conversion to sulfur, avoiding the formation of solid sulfur. Sulfur is therefore recovered in liquid form. The process, regardless of good performance, is limited by different difficulties:

The thermodynamic equilibrium of the reaction is such that the reaction is never complete. Sulfur hydrogen and sulfur dioxide remain in equilibrium with the sulfur and water formed. Typically, the amount of unreacted sulfur present in unreacted H2S and SO2 in the waste gas treatment effluenteration corresponds to approximately 0.2% to 0.5% by weight of the total sulfur in the Claus unit charge. A better conversion can be considered at a lower operating temperature, but this temperature should be kept above the sulfur freezing point F (approximately 120 ° C), otherwise the reactor would be blocked by solid sulfur;

the presence of undivided liquid sulfur in the contactor reactor, which is activated in the solvent and the circulating catalyst, which will be cycled in the contactor reactor. In fact, all liquid sulfur droplets are not separated from the solvent and the presence of liquid sulfur irreversibly triggers the presence of gaseous sulfur in the effluent due to the sulfur vapor tension. For example, the amount of unrecovered sulfur attributable to its vapor tension is approximately 0.1% by weight of sulfur from the initial charge.

Different tail gas treatment processes or TGT ("Tail Gas Treatment" according to Anglo-Saxon terminology) were developed from the 1960s onwards based on the continuation of the lower temperature Clausa reaction (125 - 160 ° C) over a solid catalyst. For example, Sulfreen®, CBA® or MCRC® processes or the liquid phase operated Clauspol® process.

The effluent from the TGT unit contains residual H2S and SO2, as well as sulfur vapor, at a partial pressure corresponding to the voltage of the reactor temperature. Other sulphurous species formed in Claus' stiotherm and notably COS and Cs2 are also present with residuals in the TGT unit effluent after these species have been hydrolyzed to H2S in the TGT unit. The set of this residual sulfur is then transformed into SO2 at the incinerator level before being thrown into the atmosphere. Optimum operation is therefore aimed at reducing sulfur species sent to the incinerator downstream of the TGT unit.

In JP 56044844, a Claus reaction gas treatment process is described, in which the operation of the unit is optimized, thanks to the determination of the H2S / SO2 ratio, which is being carried out from the Claus type unit. The determination is made by in-line analysis by measuring the gas SO2 content on the one hand and the total H2S eSO2 content on the other, thanks to the oxidation of H2S. A control valve allows you to adjust the gas flow rate at the Claus reactor contactor input to maintain the H2SZSO2 ratio at the contactor reactor output at 2. Thus, the Claus reaction can occur in good condition as the contactor reactor operates at stoichiometric conditions. According to the process described in JP56044844, the sulfur content of the waste gases is still a few percent. This patent does not consider the use of a waste gas treatment, allowing to achieve the yields achieved by the process, according to the invention.

US 4836999 combines a Claus-type treatment and a waste gas treatment, in which the H2S / SO2 ratio is measured at the entrance of the TGT unit (or at the Claus outlet), which allows the amount of air admitted to the thermal stage of the Claus unit to maintain that ratio as close as possible to 2. In US4405593, determining the H2S / S02 molar ratio at the output of the Claus unit allows for keeping the ratio as close as possible to 2 at the entrance of the TGT unit by H2S supply or SO2, either at the residual gas level or before Claus' last catalytic stage.

In the two preceding cases, the control of the ratio is made up of the TGT unit. In addition to the H2S and SO2 species present, other sulphurous species such as COS and Cs2 formed at the Claus level can be spotted in significant quantities at the entrance of the TGT unit. Hydrolysis of these species at the TGT unit level then releases a secondary H2S, yielding an excess of H2S over the optimal stoichiometry H2S / SO2 = 2. By applying the process of the invention, it is possible to improve the yield of the TGT unit and consequently, the overall yield of the sulfur recovery chain and therefore noticeably improve the gas purification rate, as yields of 99.5 wt% sulfur, even 99.8 wt%, can be obtained. Sulfur scavenging performance is optimized for both COSe Cs2 contents as the H2S / S02 molar ratio is kept closer to 2 which allows Claus to react optimally along the chain, comprising the Claus and the TGT unit.

Description of the Invention

The invention relates to a desulphurization process of a sulfur hydrogen-containing gaseous effluent using a Claus treatment unit followed by a Claus waste gas treatment unit (also called a TGT unit), which process comprises using an in-line analysis device. the H2S / SO2 molar ratio at the output of the TGT unit and a control loop, allowing the H2S / SO2 ratio to be maintained at the TGT unit output at a value between 1.5 and 2.5. By the term "close to 2" is meant that the H2S / SO2 molar ratio is regulated around the value 2, and is generally from 1.5 to 2.5, preferably from 1.7 to 2.3, of most preferably between 1.75 and 2.25, even 1.8 and 2.2.

Following description, unless otherwise stated, the percentages are expressed in volume (% volume or% vol.) And the ppm (parts per million) are also expressed in volume ppm (ppm or ppm vol.). In a Claus unit, sulfur hydrogen reacts on sulfur dioxide. The Claus unit generally contains three stages, the sulfur dioxide produced by oxidation of the sulfur hydrogen at a 0-temperature thermal stage at an elevated temperature generally between 1000 and 2000 ° C, preferably on the order of 1400 ° C, the Claus reaction. having occurred in two catalytic stages, in which the temperature is generally between 150 and 300 ° C, preferably between 200 and 250 ° C.

The gas collected at the Claus unit exit also contains sulfur hydrogen and sulfur anhydride which are still very important in pouring the gas into the atmosphere. It is therefore still necessary to treat the effluent from the Claus unit (waste gas) in a residual gas treatment unit (TGT unit). On leaving the TGT unit, for example, and preferably a unit marketed under the name Clauspol®, a purified gas is recovered and then sent to an incinerator before being discharged into the atmosphere. In accordance with the invention, the following is described with reference to Figures 2 and 3, Figure 1 being relative to the prior art.

According to Figure 1 (according to the prior art), a flowable (1), containing mainly sulfur hydrogen and may contain water, nitrogen and CO2 vapor, as well as other impurities such as ammonia and / or hydrocarbons, is sent in the stage. thermal power of a Claus unit (3). An air flow carried along a line (2) is also allowed in the thermal stage of Claus, allowing the partial combustion of sulfur hydrogen to form sulfur anhydride. The thermal stage is generally followed by two or three catalytic stages, in which the reaction of Claus proceeds, and which is therefore part of the Claus unit (3). Sulfofeliquid is recovered after condensation between the different reactors and is extracted by a line (4). The fraction recovered from the Claus unit (3) generally represents 90 to 97% of the sulfur present in the filler to be treated (1) as sulfur hydrogen.

At the outlet of the Claus unit, the waste gas extracted by a line (5) is fed into a treatment unit (TGT unit) (6). Line gas 5 generally contains 1 to 2 volume% H2S and SO2 and generally contains above 300 to 1000 ppm volume sulfur vapor. The sulfur content in line (5) is analyzed in terms of H2S and SO2 contents. The in-line analyzer (20) therefore allows the monitoring of the H2S / SO2 molar ratio. A regulating circuit allows this ratio to be kept at a value close to 2 and between 1.5 and 2.5, acting on the secondary air flow regulated by the valve (32). The secondary air flow comes complete with the primary air flow, regulated by valve (31), this valve itself being controlled from the acid gas and arp flow controller (22) and in-line analyzer. (25) H2S concentration in the acid gas. On leaving the TGT unit (6), a purified gaseous effluent is extracted by a line (8) and the formed sulfur is evacuated by a line (7).

Figure 2 depicts a first embodiment of the invention. It incorporates elements of figure 1, notably elements (1) to (8), (16), (22), (25) (31) and (32).

The effluent (8) at the TGT unit outlet (6) contains H2S, SO2, but also sulfur vapor, as well as COS and Cs2 with residual contents. Some of this effluent is removed and sent to a trapdoor trap (9). ), then to the inline analyzer (21). The in-line analyzer (21) disposed at the sulfur trap door (9) allows the valve (32) to be adjusted. The sulfur trap (9) comprises a compartment containing a porous solid layer to allow condensation of the largest sulfur vapor part, preventing condensation of water contained in the effluent to be analyzed. The effluent drawn at line level (8) is maintained at the reactor-contactor operating temperature, generally between 125 and 160 ° C until a portion of that effluent is introduced into the trapdoor trap door. The trapdoor head is also kept at a temperature, generally between 125 and 160 ° C, to prevent any solid sulfur deposits upon entering the trapdoor which would lead to a trap door. The solid layer comprising the porous solid is maintained at a temperature of from 75 to 100 ° C, thanks for example to a circulation of hot water in a double wrap around the compartment.

The porous solid layer in the housing is, for example, made up of ceramic or alumina spheres and Rashig rings, providing an important exchange surface. The vapor-depleted gas to be analyzed is extracted from the compartment by a deep immersion pipe from the compartment after passing through the porous solid layer.

According to the invention, the gas to be analyzed contains approximately 15 ppm vol. of sulfur vapor. Analysis is performed by UV spectrophotometry. H2S and SO2 have an absorbance at 228 and 280 nm respectively. For these two wavelengths, sulfur vapor presents an important interference. For a typical gas composition at the TGT unit outlet, namely 400 ppm vol. H2 S, 200 ppm vol. SO2, a residual content of 15 ppm vol. sulfur vapor contributes approximately 10% of the total absorbance of sulfur species at the two characteristic wavelengths of H2S and SO2. This level of interference is comparable to that commonly observed for waste gas analysis, H2S and SO2 osteores being closer to 1% by volume, and sulfur evaporation to 250 ppm vol.

The sulfur trap (9) using Figure 2 thus makes it possible to determine by an in-line analysis of the molar H2S / SO2 exit from the TGT unit and the secondary air regulation from the measure of that ratio. This sulfur trapdoor provides a noticeable improvement over the state of the art.

In industrial in-line analyzers, an integrated sulfur trapdoor allows a portion of the sulfur vapor to be removed by condensation of the liquid sulfur at about 115 ° C. The liquid sulfur is thus evacuated continuously by gravity and entrained by the gaseous flow at the heated sampling loop returning to the withdrawal point. This type of condenser becomes useless thanks to the use of the freeze trap hatch described earlier. This has two major advantages over the prior art.

Firstly, lowering the cold point from 125 ° C to 75 ° C allows the sulfur vapor tension to be reduced from 250 ppm vol. at 15 ppmvol., which makes it possible to analyze H2S and SO2 at the TGT unit output without major interference with sulfur vapor. Indeed, at 250 ppm vol. sulfur represents approximately 70% of the total absorbance of sulfur species at the measurement wavelengths of H2S and SO2; This contribution is reduced to 10% of total absorbance, dropping to 15 ppmvol. the concentration in sulfur vapor.

Secondly, trapped sulfur accumulates in the trapdoor under solid form. This trapdoor configuration limits the risk of plugging associated with reflux of liquid sulfur in the sampling line to the point of withdrawal.

Figure 3 depicts a preferred embodiment of the invention. According to this embodiment, the measurement of the H2S / SO2 ratio is taken at the same time at the output of the Claus (3) unit and at the output of the TGT (6) unit. In this way, the H2S / SO2 stoichiometry is controlled to maintain this molar ratio at about 2 ° C along the sulfur chain, thus ensuring optimum sulfur removal yield conditions. Figure 3 incorporates elements from Figure 2 with respect to elements (1) to (9) (16), (21), (22), (25) (31) and (32). also the analyzer (20) of figure 1.

A portion of the gaseous flow (1) representing approximately 0.5 to 2% of the total flow is sent through line (11) over a furnace (12) for a total oxidation of H2S to SO2. The effluent flow (11) is regulated by the valve (36) to represent a fixed fraction of the total flow rate (1) measured by the flow controller (23). The flow of air admitted to the furnace (12) by line (13) is regulated by the valve (33), controlled by the flow controller (24) and the in-line analyzer (25), indicating the concentration in H2S. A portion of the effluent from the furnace (15) may be sent downstream of the Clauses through the valve opening (34), the remainder of the effluent (14) is admitted to the Claus thermal stage level with the flow (1) and the air flow (2). The inline analyzer (20) measures the H2S / SO2 ratio of effluent (5) at Claus outlet. A regulating circuit allows this ratio to be kept close to value 2 by acting on the secondary air flow regulated by the valve (32). Secondary air flow completes the primary air flow, regulated by the valve (31), this valve itself being controlled from the measured acid gas and air flow by the flow controller (22) and the in-line analyzer. (25) H2S concentration in the acid gas.

The in-line analyzer (21) allows determining the effluent H2O / SO2 ratio value (8) at the exit of the TGT unit after passing through the sulfur trap (9). A regulating circuit allows maintaining this H2S / SO2 ratio by acting on the effluents (10) and (15) that come to mix with the Claus (5) effluent, the resulting effluent (17) is sent to the TGT unit (6). Measured by the analyzer (21) a H2S / S02 molar ratio greater than 2 results in valve opening (34) and complete valve closure (35). Thus, an excess of SO2 increases at the TGT unit inlet to establish this ratio at a value close to 2, generally between 1.5 and 2.5 at the TGT unit outlet. In contrast, a measurement by the analyzer (21) of an H2S / S02 ratio of less than 2 results in the valve opening (35) and the complete closing of the valve (34). An excess of H2S is then added to the TGT unit input to reset this ratio to a value close to 2 at the TGT unit output.

An additional advantage of the scheme of FIG. 3 over that of FIG. 2 is that it maintains optimum throughput by independently controlling the H2S / SO2 ratio at the Clause output at the TGT unit output. Thus it is possible to maintain a 2 + 0.5 molar H2S / SO2 ratio at the output of the TGT unit, ensuring optimum throughput of the chain assembly. In addition, it is also possible to maintain a value of between 1.5 and 2.5, preferably between 1.8 and 2.2, even between 1.9 and 2.1, the Claus output ratio and maintaining thus the Claus unit in optimal working condition.

In short

The invention relates to a sulfur hydrogen-containing gaseous effluent desulphurization process using a Claus treatment unit followed by a Clus residual gas treatment unit said TGT unit, which process comprises the use of an H2S ratio on-line analysis device. / S02 of this TGT unit and a regulating circuit, allowing to maintain this H2S / S02 ratio of gaseous effluent at the outlet of this TGT unit at a value between 1.5 and 2.5.

Preferably, this H2S / SO2 ratio at the output of the TGT unit is maintained at a value of 1.7 to 2.3.

Preferably, the gaseous effluent from the TGT unit is sent to a sulfur trap.

More preferably, the gaseous effluent exiting the TGT-unit is maintained at the operating temperature of the Claus reaction zone until such gaseous effluent is introduced into the sulfur trap door, and most preferably that sulfur trap hatch comprises. a compartment comprising a porous solid layer maintained at a temperature of 75 to 100 ° C.

According to this preferred embodiment of the process, according to the invention, a gaseous stream (1), containing mainly sulfur hydrogen and containing water vapor, nitrogen and CO2 is sent to the thermal stage of a Claus unit. (3), a flow of air carried through a line (2 after 16) is also allowed in the thermal stage of Claus1 allowing to perform the partial combustion of sulfur hydrogen to sulfur dioxide, the thermal stage is followed by two or three catalytic stages in the where Claus's reaction proceeds and is therefore part of the Claus unit (3), the liquid sulfur is recovered after condensation between the different reactors and is extracted by a line (4) at the exit of the Claus unit, the waste gas extracted by a line (5) is introduced into a treatment unit (TGT unit) (6), the sulfur formed is evacuated by a line (7), a portion of the effluent from the TGT unit (8) is removed and is sent to a trap door with sulfur (9), then to the in-line analyzer (21), the in-line analyzer (21) allows to regulate the valve (32), the effluent removed at the level of line (8) is kept at contactor reactor operation at 125 to 160 ° C until a portion of that effluent is introduced into the trap door is maintained at a temperature of 125 to 160 ° C, the porous solid is maintained at a temperature of 75 to 100 ° C, thanks to the circulation of hot water in a double wrap around the compartment, a regulating circuit allows the H2S / S02 molar ratio to be maintained between 1.5 and 2.5, acting over this secondary air flow regulated by the valve (32), the secondary air flow completes the primary air flow regulated by the valve (31), this flow itself being controlled from the gas flow measurement. acid and air flow controller (22) and in-line analyzer (25) H2S concentration in the acid gas.

According to another more preferred embodiment of the process according to the invention, a gas stream (1) containing mainly sulfur hydrogen and which may contain water vapor, eCO2 nitrogen is sent in the thermal stage of a Claus unit. (3), a portion of the gaseous effluent (1) representing approximately 0.5 to 2% of the total flow rate is sent by line (11) over a furnace (12) for a total oxidation of H2S to SO2, the effluent flow ( 11) is regulated by valve (36) so as to represent a fixed fraction of the total flow rate (1) measured by the flow controller (23), the flow of air admitted to the furnace (12) by line (13) is regulated by the valve (33), commanded by the flow controller (24) and the inline analyzer (25), indicating the H2S concentration, an effluent part of the furnace (15) is sent downstream of the Claus by opening the valve. (34), the remaining part of the effluent (14) is allowed at Claus's flow (1) and air flow (2 after 16), the on-line analyzer (20) measures the H2S / SO2 ratio of effluent (5) at the Claus outlet, a regulating circuit allows this ratio to be kept close to the value 2 while still operating. the secondary air flow regulated by the valve (32), the secondary air flow completes the primary air flow regulated by the valve (31), this valve itself being controlled from the gas and air measurement by the flow controller. (22), and the in-line analyzer (25) of H2S concentration in the acid gas, the in-line analyzer (21) allows to determine the value of the effluent (8) H2S / S02 ratio at the output of the TGT unit after passage through the trap door with sulfur (9), a regulation circuit allows maintaining this H2SZSO2 ratio, acting on the effluents (10) and (15) that come to mix with the Claus (5) effluent, the resulting effluent (17) is sent to the TGT unit. (6), the measurement by the analyzer (21) of an H2S / SO2 molar ratio greater than 2 results in the opening of the valve (34) and complete valve closure (35), in contrast, a measurement by the analyzer (21) of an H2S / S02 ratio of less than 2 results in valve opening (35) and complete valve closure (34). ).

Most preferably, the H2S / SO2 in-line analysis device is gas chromatography.

The scope of the invention will be better understood with reference to the following examples.

Examples

Example 1 (not in agreement) A previously desulphurized gaseous flow in a Clus unit (3) with a sulfur elimination yield of 93% is introduced into a TGT unit (6) with a flow rate of 550 kmol / h. This gaseous flow contains water vapor (34 vol%), carbon dioxide (4 vol%), as well as sulfur compounds: H2S (1.2 vol%), SO2 (0.6 vol%). .), COS (1000 ppm vol.), Cs2 (2000 ppm vol.), As well as sulfur vapor (1000ppm vol.), The complement consists of nitrogen.

The Claus (3) unit used is a well-known technical unit. It comprises three stages, of which 1 thermal stage and two catalytic stages.

The TGT unit (6) used is a Clauspol® unit, whose operating conditions are adapted so that the COS and Cs2SO3 compounds are 90% hydrolyzed.

The determination of the H2S / SO2 ratio at the output of the Claus unit (3) and its adjustment around the value 2 per action on the air flow allowed in the Claus thermal stage (according to the scheme of figure 1) leads to a yield. of 77.1% TGT unit sulfur is a global sulfur chain yield of 98.5% by weight.

Column 1 of Table 1 below summarizes the composition of gaseous effluent at the inlet and outlet of the TGT unit (6) as well as the sulfur yields obtained.

Example 2 (according to the invention)

The same gas flow from a Claus (3) unit as in example 1 and the same Clauspol ™ (6) unit are used in this example. This example differs from example 1 in that the scheme and mode of regulation of the H2S / SO2 ratio employed correspond to those of figure 2.

The determination of the H2S / SO2 ratio allowing its adjustment around the value 2 is made at the exit of the TGT unit (6), after passing an effluent fraction in a sulfur trap (9), whose compartment comprises an alumina ball solid kept in T = 85 ° C, then analyzed by an ultraviolet analyzer (11). Adjustment by increasing the airflow allowed in the Claus thermal stage (according to the scheme of Fig. 2) leads to a sulfur yield of the TGT unit of 91.8%, or an overall sulfur chain yield of 99, 5% by weight.

Column 2 of Table 1 below summarizes the composition of gaseous effluent at the inlet and outlet of the TGT unit as well as the sulfur yields obtained.

Example 3 (according to the invention)

The same gas flow from a Claus (3) unit as in example 1 and the same Clauspol® (6) unit are used in this example. This example differs from example 1 in that the scheme and mode of regulation of the H2S / SO2 ratio employed correspond to those of figure 3.

The determination of the H2S / SO2 ratio allowing it to be set to around 2 is done at the same time as leaving Claus (3) and leaving TGT (6) after passing a fraction of the effluent into a sulfur trap (9). ), the compartment of which comprises an alumina ball solid maintained at T = 85 ° C, then analyzed by an ultraviolet analyzer (21). Regulation of supply of SO2 to the Claus effluent (according to the scheme of Figure 3) leads to a sulfur yield of the TGT unit of 93.9%, or an overall sulfur chain yield of 99.6% by weight.

Column 3 of Table 1 below summarizes the composition of gaseous effluent at the inlet and outlet of the TGT unit as well as the sulfur yields obtained.

<table> table see original document page 15 </column> </row> <table> <table> table see original document page 16 </column> </row> <table>

Claims (8)

1. Desulfurization process of a gaseous effluent containing sulfur hydrogen using a Claus treatment unit followed by a Claus waste gas treatment unit referred to as a TGT unit, said process comprising the use of an inline H2S / SO2 ratio analyzer. gaseous effluent at the outlet of this TGT unit at a value between 1,5 and 2,5 The process according to claim 1, wherein the H2 S / SO2 ratio at the exit of the TGT unit is maintained at a value of from -1.7 to 2.3. Process according to one of claims 1 or 2, wherein the gaseous effluent from the TGT unit is sent to a sulfur trap. The process according to claim 3, wherein the effluent gas at the outlet of the TGT unit is maintained at the operating temperature of the Claus reaction zone until such gaseous effluent is introduced into the trap door with sulfur. Process according to one of claims 3 and 4, wherein said sulfur trap comprises a compartment comprising a porous solid layer maintained at a temperature of between 75 and 100 ° C. A process according to claim 1, wherein a flow gas (1) containing mainly sulfur hydrogen and which may contain water vapor, nitrogen and CO2 is sent in the thermal step of a Claus unit (3), an air flow carried by a line (2, then 16) is also allowed in the Claus thermal step, allowing partial combustion of sulfur hydrogen to form sulfur anhydride, the thermal stage is followed by two or three cataptic stages, in which Claus's reaction proceeds. , which is therefore part of the Claus unit (3), liquid sulfur is recovered, after condensation, between the different reactors and is extracted by a line (4) at the outlet of the Claus unit, the residual gas extracted by a line (5) is introduced into a treatment unit (TGT unit) (6), the formed sulfur is evacuated by a line (7), a portion of the TGT unit effluent (8) is withdrawn and is sent to a sulfur trap (9), then for the analys (21), the in-line analyzer (21) permits regulating the valve (32), the effluent drawn at line level (8) is maintained at the reactor-contactor operating temperature of 125 to 160 ° C until If a portion of this effluent is introduced into the sulfur trap door, the trap head is maintained at a temperature of 125 to 160 ° C, the porous solid is maintained at a temperature of 75 to 100 ° C, thanks to to a hot water circulation in a double wrap around the compartment, a regulating circuit allows the H2S / SO2 molar ratio to be maintained between 1.5 and 2.5 while acting on the secondary air flow regulated by the valve (32). ), the secondary air flow completes the primary air flow regulated by the valve (31), this valve itself being controlled from the acid gas and air flow measurement by the flow controller (22) and the online concentration analyzer (25) H2S in the acid gas. A process according to claim 1, wherein a flowable (1) containing mainly sulfur hydrogen and capable of containing water vapor, nitrogen and CO2 is sent at the thermal stage of a Claus (3) unit, a Part of a gaseous effluent (1) representing approximately 0.5 to 2% of the total flow is sent through line (11) over a furnace (12) for a total oxidation of H2S to SO2, the effluent flow (11). is adjusted by the valve (36) to represent a fixed fraction of the total flow rate (1) measured by the flow controller (23), the flow of air fed into the furnace (12) by line (13) is controlled by the valve (33), controlled by the flow controller (24) and the inline analyzer (25) which indicates H2S concentration, a portion of the furnace effluent (15) is sent downstream from Claus through the valve opening ( 34), the remaining part of the effluent (14) is admitted at Claus thermal stage level with flow (1) and air flow (2, then 16) , the in-line analyzer (20) measures the H2S / S02 ratio of the effluent (5) at Claus outlet, a regulating circuit allows to maintain this near ratio of value 2 by acting on the secondary air flow regulated by the valve (32), the Secondary air flow completes the primary air flow, regulated by valve (31), this valve itself being commanded from the measurement of acid gas and air flow by the flow controller (22), and the analyzer in In line (25) of the H2S concentration in the acid gas, the inline analyzer (21) allows to determine the value of the H2S / SO2 ratio of the effluent (8) at the exit of the TGT unit after passing through the trap door with sulfur (9). allows the H2S / SO2 ratio to be maintained by flowing over effluents (10) and (15) and mixing with the Claus (5) effluent, the resulting effluent (17) is sent to the TGT unit (6) at measured by the analyzer (21) of a H2S / S02 molar ratio greater than 2 triggers the valve opening (34) and the closing with In contrast to the valve (35), a measurement by the analyzer (21) of an H2S / SO2 ratio of less than 2 results in valve opening (35) and complete valve closure (34). Process according to one of claims 1 to 7, wherein the H2S / SO2 ratio on-line analyzer is gas chromatography.